3-chloro-1,2-propanediol (3-MCPD) is a well known organic chemical compound formed in foods. It is a byproduct of food processing, especially in heat processed, fat-containing foodstuff, where 3-MCPD is formed during the processing.
Recent studies have identified high levels of 3-MCPD esters in refined fats and oils, including edible oils. 3-chloro-1,2-propanediol (3-MCPDs) and their esters have been found in all refined vegetable oils. The processing and refining of oils leads to formation of these unwanted byproducts, organohalo species (for example, 3-chloro-1,2-propanediol (MCPDs)) and glycidol and their respective esters. Free MCPD has been found to exhibit genotoxic and carcinogenic effects in testing, and these effects have raised some concern, especially in the food industry. Glycidol is also a known genotoxic and carcinogenic compound. No toxicological profiles are known for the 3-MCPD esters or glycidyl esters. These esters' toxicities depend on their breakdown by lipases in the gut to the free 3-MCPD or glycerol species, which is a current area of concern and study.
Currently, there is limited and contradictory knowledge available about when and how 3-MPCD-esters are formed during the oil refining process. The highest 3-MPCD ester contents are found in refined oils whereas virgin or non-refined oils have lower content, sometimes below detection limits. There is some belief that heat pre-treatment of the seed (or fruit) may contribute to the levels in non-refined oils. Research into the mechanism of 3-MCPD/glycidol-ester formation is ongoing in the field.